Performance Optimization Vitalii Topoliuk @vtopoliuk 

- Performance scenarios - How to measure performance - How to improve key scenarios - Tips and Tricks Contents: 

- Not just about speed - CPU tasks - Memory - Rendering - File I/O - Networking - Power Performance Performance scenarios 

- Not just about speed - CPU tasks - Memory - Rendering - File I/O - Networking - Power Performance Performance scenarios 

Overall recommendations Performance scenarios - Don’t guess, just measure - Measure on slowest device - Measure on pessimistic data - Measure on real data 

How to measure Performance scenarios - Instruments - Logging - Quartz Debug (OS X) 

CPU Performance Optimization 

- Unhappy users CPU CPU Tasks Optimization 

- Unhappy users - System can abort your app CPU CPU Tasks Optimization 

Time Profiler Demo CPU Tasks Optimization 

CPU Tasks Optimization 

CPU Tasks Optimization 

- do less work - do work later - do slow in background and use placeholders - do work faster Main strategies CPU Tasks Optimization 

Memory Performance Optimization 

- Crashes => Unhappy Users Memory Memory Optimization 

Allocations & Leaks Demo Memory Optimization 

Memory Optimization 

Memory Optimization 

Memory Optimization 

- do less work - do work later - break down work to smallest batches - use ARC :) - @autoreleasepool Main strategies Memory Optimization 

.nib loading Tips and Tricks x10 faster 

ARC vs MMM Tips and Tricks - (void)getPoints:(DPoint[2])outPoint forCenterPoint:(DPoint)centerPoint targetingVector: (DVector)targetingVector skipEquation:(BOOL)skip lineWidth:(DFloat)lineWidth { DVector normVector = DVectorNormalVector(targetingVector); DFloat originX = centerPoint.x + (lineWidth / 2.0f) * normVector.x; ... // some code outPoint[1] = (DPoint){originX, originY}; } 

ARC vs MMM Tips and Tricks x5 faster on MMM - (void)getPoints:(DPoint[2])outPoint forCenterPoint:(DPoint)centerPoint targetingVector: (DVector)targetingVector skipEquation:(BOOL)skip lineWidth:(DFloat)lineWidth { DVector normVector = DVectorNormalVector(targetingVector); DFloat originX = centerPoint.x + (lineWidth / 2.0f) * normVector.x; ... // some code outPoint[1] = (DPoint){originX, originY}; } 

Universal solutions Tips and Tricks [self.array addObject:[NSValue valueWithCGPoint:point]] xxx times faster VS @interface DPointsCollection : NSObject - (void)addPoint:(CGPoint)point atIndex:(NSUInteger)index; - (void)removePointAtIndex:(NSUInteger)index; ... @end 

Sorted NSArray Tips and Tricks [self.array addObject:object]; [self.array sortUsing...]; 

Sorted NSArray Tips and Tricks NSUInteger index = [self.array indexOfObject:object inSortedRange:range options:NSBinarySearchingInsertionIndex usingComparator:comparator]; [self.array insertObject:object atIndex:index]; 

Delay large tasks Tips and Tricks - (void)addPerson:(DPerson*)person { ... [self save]; // large task } - (void)addBook:(DBook*)book { ... [self save]; // large task } 

Delay large tasks Tips and Tricks - (void)addPerson:(DPerson*)person { ... [self delayedSave]; } - (void)addBook:(DBook*)book { ... [self delayedSave]; } - (void)delayedSave { [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(save) object:nil]; [self performSelector:@selector(save) withObject:nil afterDelay:0.1f]; } 

API Levels Tips and Tricks - try high level API first - then try lower level NSArray => CFArray => void* NSXMLParser => libxml 

Questions & Answers Performance Optimization